High-frequency concentric line oscillator



X/ :n ig/Nei) June 7, 194g. E FUBlNl ET AL 2,472,204

HIGH-FREQUENCY CONCENTRIC LINE OSCILLATOR Filed March l, 1946 FIG! EUGENE FUBINI HEGAR G.KRIEGEL BY JOHN G.$TEPHENSON A TTEWE Y Patented `lune 7, P1949 SEARCH E? HIGH-FREQUENCY CONCENTRIC LINE OSCILLATOR Eugene Fubini, New York, N. Y., Hegar C. Kriegel,

Houston, Tex., and John G. Stephenson, Mineola, N. Y., assignors to the United States of America as represented by the Secretary of War Application March 1, 1946, Serial No. 651,310

(Cl. Z50-36) 4 Claims.

1 This invention relates in general to electrical generators and more particularly to high-frequency oscillators.

lines or resonant cavities for the tuning circuits @instead of conventional inductance-capacitance ri circuits. vThis invention relates to an oscillator which uses resonant cavities of the so called coninvention to provide a high-frequency oscillator, i which utilizes resonant cavities for its tuning cir- Elcuits, said cavities being constructed in a concentric manner.

It is a further object of this invention to provide a high-frequency oscillator with a plurality of resonant cavities tunable by a single control.

It is a still further object of this invention to provide a high-frequency oscillator tunable over a relatively wide frequency range.

In general, this invention contemplates the use of three concentric hollow cylinders which form two coaxial cavities, the latter being used as resonant circuits, This oscillator is particularly adapted for use with the lighthouse type of vacuum tubes. The tube is mounted in the smaller cylinder, and the outer cavity is the resonant circuit between grid and plate. The inner cavity forms a resonantcircuit between cathode and grid. Means are provided for tuning both cavities simultaneously. yvlmoupling between the two cavities is accomplished bybothmagnetic and elec: trostatic ouplingmeans.

Other objects, features and advantages of this invention will suggest themselves to those skilled in the art and will become apparent from the following description of the invention taken in connection with the accompanying drawing, in

which:

Fig. 1 is a cross-sectional view of the oscillator; and

Fig. 2 is an equivalent schematic circuit diagram of the invention.

Referring now more particularly to Fig. 1, metallic hollow cylinders II, I3, and I5 are constructed and arranged concentricalli7 as shown. Another hollow metallic -cylinder I1 is attached inside the cylinder II by means of one or more screws I9 or other appropriate fasteningV means. -A-Washer or bushing of insulating material centric type and it is an object, therefore, of this --lo electrically insulates the screw I9 from cylinder I I. A dielectric material 2I is interposed between the cylinders I I and I1 A vacuum tube 23 of the lighthouse type is placed in the cylinder I1, as shown, being held in place by tube socket 25, which is connected to cylinder I1 in any conventional manner. An annular spring clip 21 is connected inside the cylinder I1 and electrically connects the cathode shell 29 of lighthouse tube 2 3 to cylinder I1. A metallic circular plate 3I having spring metal fingers 33 electrically connects the grid connection 35 of the lighthouse tube 23 to the cylinder I3. Electrostatic coupling probes 31 and magnetic coupling loops 39 are used to couple energy between the two cavities. An annular metallic plate 4I is connected to the cylinder I5. Annular metallic plate 43 is connected to plate 4I by screws 45. Insulating washers 41 electrically insulate the screws 45 from plate 43. A dielectric material 49 is interposed between plates 4I and 43. Plate 43 has spring metallic iingers 5l similar to plate 3I which electrically connect the plate connection 53 to plate 43. Annular pistons 55 and 51 electrically short the inner and outer cavities. Rods 59 and 6I are used to move pistons 55 and 51 back and forth in a longitudinal direction. Well known mechanical coupling means between rods -59 and 6I are provided whereby the pistons 55 and 51 may be moved simultaneously. Means also are provided Whereby the position of one rod may be changed independently of the other rod. In practice, the rods and supports are threaded whereby when rotated the rods will move in a longitudinal direction.

' Also, the rods are geared together so that both pistons move simultaneously. Movement of one piston only is accomplished by unmeshing the gears. Coaxial transmission line 63 is inserted into the outer cavity with its center conductor terminating in an electrostatic probe 65. Means are provided for moving the line 63 in an axial direction and the probe 65 in a radial direction. The anode cooling fins 61 and the metal plate 69 form a capacitor, and means are provided for Y -adjusting the distance between them. In pracif v grid capacitance of lighthouse tube 23 and other inherent capacitances can be represented by the tuned circuit consisting of inductance 1| and the capacitor 13 connected between the grid 14 and the cathode 'l5 of lighthouse tube 23.

The outer coaxial cavity and the grid-plate capacitance of lighthouse tube 23 and other inherent capacitances may be represented by the tuned circuit of inductance 16 and capacitor 11 connected between grid 14 and anode or plate 18. The capacitor formed by cylinders Il and l1 and dielectric 2|, as shown in Fig. 1, can be represented by capacitor 18. The capacitor formed by plates 4I and 43 and dielectric 49 can be represented by capacitor 8l. Cathode-plate capacitance and other stray capacitances are represented by capacitor 83. The plate 18 is connected through an inductance 85 to a source of positive potential (not shown). The cathode is connected to ground. The grid 14 is returned to ground through resistor 81. The capacitor formed by fins 61 and plate B9 is not shown in Fig. 2 but will be explained later. Actually, the grid of the oscillator shown in Fig. 1 is grounded, but for clarity the cathode is shown grounded in Fig. 2.

It can be seen that the circuit of Fig. 2 can be considered as a form of a Colpitts oscillator. Since the theory of this general type of oscillator is well known in the art, no explanation will be given as to its theory of operation.

In operation, the frequency of the oscillator is controlled by the positions of the pistons 55 and 51. Oscillation is possible in several different modes and the tuning range is thereby in- Y creased. The fundamental mode of operation is such that both the grid-plate and cathode-grid pistons are adjusted in such a manner that the coaxial cavities are substantially one-quarter wavelength long. By readjusting the relative positions of the pistons other modes of operation may be obtained.

It was found that by shifting the grid-cathode plunger slightly when in the one-quarter wavelength mode, the mode will be changed to the three-quarter wavelength mode. Mode separation was made adequate by choosing the product CZo for the grid-plate, line to differ as much as possible from CZo for the grid-cathode line where C is the grid-plate capacitance Zo is the characteristic impedance of the gridplate line C is the grid-cathode capacitance Zo is the characteristic impedance of the grid cathode line The combined electrostatic and magnetic feedback will then enable operation in both the onequarter wavelength mode and in the three- -quarter wavelength mode without making any changes other than shifting the grid-cathode plunger.

At a certain frequency within the tuning range l of the oscillator, the cooling fins 61 become resoback properly over the entire tuning range, a plurality of magnetic coupling loops and electrostatic coupling probes are constructed in the plate 3|.

Output power is taken from the oscillator at coaxial transmission line 53 by means of probe 65. Means are provided for moving the line 63 and probe 65 in an axial direction, and for moving the probe in a radial direction whereby optimum coupling may be obtained over the entire range.

While there has been described what is at present considered to be the preferred embodiment of the invention, it will be obvious to those skilled in the art that various changes and modications may be made therein without departing from the scope of the invention as set forth in the appended claims and we claim all such changes and modifications as fall fairly within the spirit and scope of the invention. r .We claim:

f 1. In an oscillation generator, rst, second and tliird hollow metallic cylinders, said second cyllinder being larger than said first cylinder, and said third cylinder being larger than said second cylinder, means positioning said cylinders in a concentric manner, a lighthouse type vacuum tube, a first dielectric means, means coupling the cathode of said vacuum tube to said first cylinder through said first dielectric means, means connecting the second cylinder to the grid of said vacuum tube, a second dielectric means, means coupling said third cylinder to the plate of said vacuum tube through said second dielectric means, rst and second annular pistons, said iirst piston being positioned in the cavity formed by said first and second cylinders, said second piston being positioned in the cavity formed by said second and third cylinders, means allowing the driving of said pistons in an axial direction simultaneously, magnetic coupling means for coupling energy between the cavity formed by said rst and second cylinders and the cavity formed by said second and third cylinders, electrostatic coupling means for coupling energy between the cavity formed by said rst and second cylinders and the cavity formed by said second and third cylinders, a capacitor plate placed in the proximity of the anode of said vacuum tube, means for adjusting the proximity of said plate to said anode, coupling means inserted through said third cylinder into the cavity formed by said second and third cylinders, means for adjusting said latter coupling means in an axial direction, and means for adjusting said latter coupling means in a radial direction.

2. Apparatus in accordance with claim 1 in which operation in at least two modes is obtainable by adjustment of one of said pistons.

3. In an oscillation generator, conducting means forming a first annular resonant cavity, conducting means forming a second annular resonant cavity concentric with and disposed externally of said rst annular resonant cavity. electron tube means having at least cathode, grid and anode electrodes, means electrically coupling said first annular resonant cavity between the cathode and grid of said electron tube means, means electrically coupling said second annular resonant cavity between the grid and anode of l l i said electron tube means, -atleast a portion of the pling means between said flrst and second annusumti 8005i lar resonant cavities comprising a plurality of electrostatic probes and electromagnetic loops, means for tuning said first and second annular resonant cavities, adjustable means for deriving energy from said second cavity, means for altering the natural resonant frequency of said heat dissipating means whereby maximum output may be obtained from said oscillation generator at all frequencies of operation.

4. Apparatus in accordance with claim 3, wherein said means for altering the natural resonant frequency of said heat dissipating means comprises a capacitor plate in proximity with said heat dissipating means and means for adjusting said proximity as required for altering 15 the natural resonant frequency.

EUGENE FUBINI. HEGAR C. KRIEGEL. JOHN G. STEPHEIIBON.

REFERENCES CITED The following references are of record in the le of this patent:

UNITED STATES PATENTS Number Name Date 2,284,405 McArthur May 26, 1942 2,287,845 Varian June 30, 1942 2,289,846 Litton July 14, 1942 2,353,742 McArthur July 18, 1944 2,408,355 Turner Sept. 24, 1946 2,409,640 Moles Oct. 22, 1946 2,412,805 Ford Dec. 12, 1946 2,416,080 Bailey Feb. 18, 194'? 2,416,565 Beggs Feb. 25, 1947 2,416,567 McArthur Feb. 25, 1947 

